Image pickup lens for solid-state image pickup element

ABSTRACT

An image pickup lens includes a first lens having a positive refractive power with a convex surface facing the object side, a second lens having a negative refractive power with a concave surface facing an image side, a third lens of a meniscus shape having a convex surface facing the object side, a fourth lens of a meniscus shape having a positive refractive power with a convex surface facing the image side, and a fifth lens having a negative refractive power with a concave surface facing the image side, wherein the both surfaces of the fifth lens have an aspherical shape, and the curvature radius of the fourth lens satisfies conditional expression (13) below: 
       1.4&lt; r 7/ r 8&lt;3.0  (13)
         where r7 is the curvature radius of the object-side surface of the fourth lens, and r8 is the curvature radius of the image-side surface of the fourth lens.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.13/203,159, filed Aug. 24, 2011, which is a national phase of PCTapplication No. PCT/JP2010/055048, filed on Mar. 24, 2010, the contentsof which are incorporated herein by reference.

The present application is based on and claims priority of Japanesepatent application No. 2009-084695 filed on Mar. 31, 2009, the entirecontents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image pickup lens for a solid-stateimage pickup element that is used in a small-size image pickup devicefor mobile terminals, PDA (Personal Digital Assistant) devices, andother small-size, thin electronic devices.

2. Description of the Related Art

In recent years, the market for mobile terminals having an image pickupdevice has grown. Consequently, the image pickup device has begun toincorporate a small-size, high-pixel-number, solid-state image pickupelement.

Corresponding to the downsizing and increase in the number of pixels ofthe imaging element, the image pickup lens is required to have increasedperformance in view of resolution and image quality, and with wide usethereof, the image pickup lens is also requested to reduce cost.

In order to satisfy a trend for increasing performance, the image pickuplens configured from a plurality of lenses is becoming popular. Incomparison with the lens configuration of two to four lenses, the imagepickup lens of a five-lens configuration which is capable of increasingperformance than in the lens configuration of two to four lenses is alsobeing proposed.

An image pickup lens disclosed, for instance, in JP-A No. 2007-264180(Patent Document 1) exhibits high performance by including, in the orderfrom an object side, a first lens, a second lens, a third lens, a fourthlens, and a fifth lens. The first lens has a convex surface on theobject side and has a positive refractive power. The second lens has aconcave surface facing an image side, has a negative refractive power,and has a meniscus shape. The third lens has a convex surface facing theimage side, has a positive refractive power, and has a meniscus shape.The fourth lens has an aspherical surface on both sides, has a concavesurface on the image side on an optical axis, and has a negativerefractive power. The fifth lens has an aspherical surface on both sidesand has a positive or negative refractive power.

Further, an image pickup lens disclosed, for instance, in JP-A No.2007-298572 (Patent Document 2) exhibits high performance by including,in the order from an object side, an aperture stop, a first lens, asecond lens, a third lens, a fourth lens, and a fifth lens. The firstlens has a positive refractive power. The second lens is joined to thefirst lens and has a negative refractive power. The third lens has aconcave surface facing the object side and has a meniscus shape. Thefourth lens has a concave surface facing the object side and has ameniscus shape. The fifth lens has at least one aspherical surface, hasa convex surface facing the object side, and has a meniscus shape.

The image pickup lenses described in the Patent Documents 1 and 2 eachinclude five lenses to exhibit high performance. From the viewpoint oftheir optical length, however, they are not adequately designed toreduce their size and thickness.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above circumstancesand has an object to provide a small-size, low-cost, high-performanceimage pickup lens for a solid-state image pickup element.

The above-mentioned problem can be addressed when the image pickup lensfor a solid-state image pickup element is configured as described below.

An image pickup lens according to aspect 1 of the present inventionincludes, in the order from an object side, a first lens, a second lens,a third lens, a fourth lens, and a fifth lens. The first lens has aconvex surface facing the object side on an optical axis and has apositive refractive power. The second lens has a concave surface facingan image side on the optical axis and has a negative refractive power.The third lens has a convex surface facing the object side on theoptical axis and has a meniscus shape. The fourth lens has a convexsurface facing the image side on the optical axis, has a positiverefractive power, and has a meniscus shape. The fifth lens has a concavesurface facing the image side on the optical axis and has a negativerefractive power. The object-side surface and image-side surface of thefifth lens have an aspherical shape, which contains at least oneinflection point from a center of the lens to a periphery thereof. Thecurvature radius of the fourth lens satisfies conditional expression(13) below:

1.4<r7/r8<3.0  (13)

where r7 is the curvature radius of the object-side surface of thefourth lens, and r8 is the curvature radius of the image-side surface ofthe fourth lens.

As the object-side surface and image-side surface of the fifth lens havean aspherical shape that contains at least one inflection point from thecenter of the lens to the periphery thereof, it is possible to obtainadequate off-axis performance and CRA.

Conditional expression (13) above defines the lens shape of the fourthlens. If the value is below the lower limit of the conditionalexpression (13), the power of the fourth lens is too weak. Consequently,performance deterioration occurs because it is difficult to correctvarious aberrations. If, on the contrary, the value exceeds the upperlimit thereof, the fourth lens has an excessively strong power or has asmall degree of meniscus curvature. In this instance, too, it isdifficult to maintain a proper aberration balance so that expectedperformance is not obtained.

The image pickup lens according to aspect 2 satisfies conditionalexpressions (1) and (2) below, which concern the Abbe number of amaterial used for the first lens and the second lens:

45<ν1<90  (1)

22<ν2<35  (2)

where ν1 is the Abbe number for d-line of the first lens, and ν2 is theAbbe number for d-line of the second lens.

Conditional expression (1) above defines the Abbe number of the firstlens. If the value is below the lower limit of the conditionalexpression (1), the variance value difference from the second lens isdecreased so that chromatic aberration correction is insufficient. If,on the contrary, the value exceeds the upper limit thereof, the balancebetween axial chromatic aberration and chromatic aberration ofmagnification is impaired so that performance deterioration occurs atthe periphery of an image area.

Conditional expression (2) above defines the Abbe number of the secondlens. If the value is below the lower limit of the conditionalexpression (2), the balance between axial chromatic aberration andoff-axis chromatic aberration is impaired so that performancedeterioration occurs at the periphery of the image area. If, on thecontrary, the value exceeds the upper limit thereof, the variance valuedifference from the first lens is decreased so that chromatic aberrationcorrection is insufficient.

The image pickup lens according to aspect 3 is configured so that thefirst lens, the second lens, the third lens, the fourth lens, and thefifth lens are so-called plastic lenses that have at least oneaspherical surface and are made of a resin material.

Cost reduction can be achieved when the first lens, the second lens, thethird lens, the fourth lens, and the fifth lens are made of aninexpensive resin material exhibiting high production efficiency.

The image pickup lens according to aspect 4 is configured so that anaperture stop is positioned on the object side of the first lens.

As the aperture stop is positioned on the object side of the first lens,it is easy to reduce a CRA (Chief Ray Angle) and obtain sufficient lightamount at the periphery of an image plane at which light amountdecreases.

The image pickup lens according to aspect 5 is configured so that thefirst lens and the second lens satisfy conditional expressions (3) and(4) below:

0.50<f1/f<1.00  (3)

−1.50<f2/f<−0.65  (4)

where f is the composite focal length of the entire image pickup lenssystem, f1 is the focal length of the first lens, and f2 is the focallength of the second lens.

Conditional expression (3) above defines the range of the focal lengthof the first lens with respect to the focal length of the entire imagepickup lens system. If the value is below the lower limit of theconditional expression (3), the focal length of the first lens is tooshort. This makes it difficult to correct spherical aberration and comaaberration. If, on the contrary, the value exceeds the upper limitthereof, the optical length is too long so that the thickness of theimage pickup lens cannot be sufficiently reduced.

Conditional expression (4) above defines the range of the focal lengthof the second lens with respect to the focal length of the entire imagepickup lens system. If the value is below the lower limit of theconditional expression (4), the power of the second lens is insufficientso that chromatic aberration cannot be adequately corrected. If, on thecontrary, the value exceeds the upper limit thereof, the focal length ofthe second lens is too short. This makes it difficult to correctspherical aberration and coma aberration, and the error sensitivityduring manufacturing becomes severe.

The image pickup lens according to aspect 6 is configured so that thefourth lens and the fifth lens satisfy conditional expressions (5) and(6) below:

0.9<f4/f<1.50  (5)

−1.70<f5/f<−0.85  (6)

where f is the composite focal length of the entire image pickup lenssystem, f4 is the focal length of the fourth lens, and f5 is the focallength of the fifth lens.

Conditional expression (5) above defines the range of the focal lengthof the fourth lens with respect to the focal length of the entire imagepickup lens system. If the value is below the lower limit of theconditional expression (5), the focal length of the fourth lens is tooshort. This makes it difficult to correct astigmatism and comaaberration, and the error sensitivity during manufacturing becomessevere. If, on the contrary, the value exceeds the upper limit thereof,chromatic aberration of magnification and astigmatism are not adequatelycorrected so that expected performance is not obtained.

Conditional expression (6) above defines the range of the focal lengthof the fifth lens with respect to the focal length of the entire imagepickup lens system. If the value is below the lower limit of theconditional expression (6), the power of the fifth lens is insufficient.This makes it difficult to decrease the optical length. If, on thecontrary, the value exceeds the upper limit thereof, it is difficult todecrease the CRA, and the error sensitivity at low image height duringmanufacturing becomes severe.

The image pickup lens described in the present invention may beconfigured so that the first lens and the third lens satisfy conditionalexpression (7) below:

−0.15<f1/f3<0.37  (7)

where f1 is the focal length of the first lens, and f3 is the focallength of the third lens.

Conditional expression (7) above defines the ratio between the focallength of the first lens and the focal length of the third lens. If thevalue is below the lower limit of the conditional expression (7), thefocal length of the third lens is negative and too short. This makes itdifficult to provide aberration correction. If, on the contrary, thevalue exceeds the upper limit thereof, the focal length of the thirdlens is positive and too short. This impairs the balance of astigmatismand the balance of coma aberration, and the error sensitivity duringmanufacturing becomes severe.

The image pickup lens according to aspect 7 is configured so that thesecond lens, the third lens, and the fourth lens satisfy conditionalexpression (8) below:

0.0<f2·3·4  (8)

where f2·3·4 is the composite focal length of the second, third, andfourth lenses.

Conditional expression (8) above defines the composite focal length ofthe second, third, and fourth lens. If the value is below the lowerlimit of the conditional expression (8), the negative power of thesecond lens is too strong so that the error sensitivity duringmanufacturing becomes too severe, or the positive power of the fourthlens is too weak so that it is difficult to correct astigmatism anddistortion.

The image pickup lens according to aspect 8 is configured so that thefirst lens, the second lens, the third lens, the fourth lens, and thefifth lens satisfy conditional expressions (9), (10), and (11) below:

f1<|f2|<|f3|  (9)

f1<f4<|f3|  (10)

f1<|f5|<|f3|  (11)

where f1 is the focal length of the first lens, f2 is the focal lengthof the second lens, f3 is the focal length of the third lens, f4 is thefocal length of the fourth lens, and f5 is the focal length of the fifthlens.

Conditional expression (9) above defines the power relationship betweenthe first lens, the second lens, and the third lens, that is, the focallength relationship. If the value is below the lower limit of theconditional expression (9), the negative power of the second lens is toostrong, so that the optical length becomes long, and the errorsensitivity during manufacturing becomes severe. If, on the contrary,the value exceeds the upper limit thereof, the power of the third lensis too strong so that it is difficult to obtain adequate off-axisperformance.

Conditional expression (10) above defines the power relationship betweenthe first lens, the third lens, and the fourth lens, that is, the focallength relationship. If the value is below the lower limit of theconditional expression (10), the power of the fourth lens is too strong,so that the optical length becomes long, and it is difficult to correctastigmatism and distortion. If, on the contrary, the value exceeds theupper limit thereof, the power of the third lens is too strong so thatit is difficult to obtain adequate off-axis performance.

Conditional expression (11) above defines the power relationship betweenthe first lens, the third lens, and the fifth lens, that is, the focallength relationship. If the value is below the lower limit of theconditional expression (11), the negative power of the fifth lens is toostrong. This makes it difficult to correct coma aberration andastigmatism. If, on the contrary, the value exceeds the upper limitthereof, the power of the third lens is too strong so that it isdifficult to obtain adequate off-axis performance.

The third lens has a weaker power than the other lenses. However, itsfront and rear aspherical surfaces effectively work to reduce anaberration caused within the second lens. Particularly, its fourth-orderaspherical coefficient effectively works and plays an important role toexhibit performance characteristics specific to a combination of fivelenses.

The image pickup lens according to aspect 9 is configured so that thecurvature radius of the first lens satisfies conditional expression (12)below:

−0.40<r1/r2<0.10  (12)

where r1 is the curvature radius of the object-side surface of the firstlens, and r2 is the curvature radius of the image-side surface of thefirst lens.

Conditional expression (12) above defines the lens shape of the firstlens. If the value is below the lower limit of the conditionalexpression (12), the optical length cannot be readily reduced. Inaddition, the error sensitivity during the manufacture of the first lensbecomes severe. If, on the contrary, the value exceeds the upper limitthereof, it is difficult to maintain a proper aberration balance so thatexpected performance is not obtained.

The image pickup lens according to aspect 10 is configured so that theoptical length and focal length of the entire image pickup lens systemsatisfy conditional expression (14) below:

1.05<L/f<1.30  (14)

where L is the distance from a front surface of the first lens to theimage plane, and f is the composite focal length of the entire imagepickup lens system.

Conditional expression (14) above defines the optical length withrespect to the focal length of the entire image pickup lens system. Ifthe value is below the lower limit of the conditional expression (14),it is difficult to correct various aberrations due to an excessivelydecreased optical length. In addition, the error sensitivity duringmanufacturing becomes too severe. If, on the contrary, the value exceedsthe upper limit thereof, it is difficult to reduce the thickness of theimage pickup lens due to an excessively increased optical length.

The image pickup lens according to aspect 11 is configured so that thediameter of the aperture stop satisfies conditional expression (15)below:

0.30<CA1/f<0.50  (15)

where CA1 is the diameter of the aperture stop, and f is the compositefocal length of the entire image pickup lens system.

Conditional expression (15) above defines the F-number (Fno), which isan indication of lens brightness. If the value is below the lower limitof the conditional expression (15), the F-number is excessively large sothat requested brightness is not achieved in most cases. If, on thecontrary, the value exceeds the upper limit thereof, the F-number isexcessively small or the distance between an aperture stop (F-numberluminous flux restriction plate) and the front surface of the first lensis excessively long. In either case, expected optical performance is notobtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an image pickup lens according to afirst embodiment of the present invention;

FIG. 2 shows various aberration diagrams of the image pickup lensaccording to the first embodiment of the present invention;

FIG. 3 is a cross-sectional view of the image pickup lens according to asecond embodiment of the present invention;

FIG. 4 shows various aberration diagrams of the image pickup lensaccording to the second embodiment of the present invention;

FIG. 5 is a cross-sectional view of the image pickup lens according to athird embodiment of the present invention;

FIG. 6 shows various aberration diagrams of the image pickup lensaccording to the third embodiment of the present invention;

FIG. 7 is a cross-sectional view of the image pickup lens according to afourth embodiment of the present invention;

FIG. 8 shows various aberration diagrams of the image pickup lensaccording to the fourth embodiment of the present invention;

FIG. 9 is a cross-sectional view of the image pickup lens according to afifth embodiment of the present invention;

FIG. 10 shows various aberration diagrams of the image pickup lensaccording to the fifth embodiment of the present invention;

FIG. 11 is a cross-sectional view of the image pickup lens according toa sixth embodiment of the present invention; and

FIG. 12 shows various aberration diagrams of the image pickup lensaccording to the sixth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will now be described by usingconcrete numerical values. In the first to sixth embodiments, the imagepickup lens for a solid-state image pickup element includes, in theorder from the object side, an aperture stop ST, a first lens L1, asecond lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, aplane-parallel glass IR, and an image plane.

In the first to sixth embodiments, the second lens L2, the third lensL3, the fourth lens L4, and the fifth lens L5 are so-called plasticlenses that have at least one aspherical surface and are made of a resinmaterial. It should also be noted that the aperture stop ST ispositioned on the object side of the first lens L1.

The object-side surface and image-side surface of the fifth lens L5 havean aspherical shape that contains at least one inflection point from thecenter of the lens to the periphery thereof. The aspherical shape ineach embodiment is expressed by the following aspherical surface formulain which the apex of a surface is regarded as the origin, the Z-axis isoriented in the direction of an optical axis, and the height in adirection perpendicular to the optical axis is h:

Z=(h2/r)/[1+{1−(1+K)(h2/r2)}½]+A ₄ h ⁴ +A ₆ h ⁶ +A ₈ h ⁸+ . . .

It Should Be Noted That The Following Symbols Are used in the aboveaspherical surface formula and in the description of each embodiment:

Ai: ith-order aspherical coefficientr: Curvature radiusK: Conic constantf: Focal length of the entire image pickup lens system

F: F-number

d: Distance between lens surfaces along axisnd: Refractive index of a lens material relative to d-lineν: Abbe number of a lens materialFurther, in the following description (including lens data in tables),the exponent of 10 (e.g., 4.5×10⁻⁰⁴) is expressed by using the letter E(e.g., 4.5E-04), and surface numbers for lens data are sequentiallyassigned so that, for example, the object-side surface of the first lensL1 is surface 1.

First Embodiment

Table 1 shows numerical data about the image pickup lens according tothe first embodiment. FIG. 1 is a cross-sectional view of the imagepickup lens. FIG. 2 shows various aberration diagrams.

TABLE 1 f = 4.815 F = 2.8 Surface Number r d nd ν K  1 (ST) 2.297 0.5501.5247 56.26 0.175  2 8384.615 0.411 0  3 −6.170 0.299 1.6142 25.582.471  4 8.586 0.242 0  5 2.383 0.481 1.5247 56.26 −7.218  6 3.460 0.658−1.443  7 −2.320 0.815 1.5094 56.00 −0.455  8 −1.502 0.217 −0.645  92.288 0.897 1.5094 56.00 −3.909 10 1.274 0.714 −3.515 11 ∞ 0.300 1.516864.20 12 ∞ 0.635 Surface Number A4 A6 A8 A10 A12 A14 A16  1 (ST)−5.423E−3 −2.923E−3 −1.511E−2 2.424E−3 −1.233E−2 3.275E−3 4.002E−3  28.525E−3 −2.136E−2 −1.410E−2 −1.071E−2 3.924E−3 0 0  3 1.427E−1−1.124E−1 5.307E−2 −1.649E−2 −1.541E−2 1.183E−2 0  4 9.163E−2 −4.267E−29.557E−3 1.336E−2 −1.497E−2 5.154E−3 0  5 −4.203E−2 −4.711E−3 −2.518E−32.523E−3 0 0 0  6 −4.458E−2 −3.915E−3 −4.687E−4 4.421E−4 0 0 0  75.934E−2 −4.778E−2 2.552E−2 −7.375E−3 9.592E−4 0 0  8 2.946E−2 −6.592E−3−1.052E−3 1.407E−3 −1.257E−4 0 0  9 −6.925E−2 1.547E−2 −1.984E−34.124E−5 2.050E−5 −1.537E−6 −5.993E−9 10 −4.400E−2 1.076E−2 −2.049E−32.486E−4 −1.983E−5 1.014E−6 −2.577E−8

Second Embodiment

Table 2 shows numerical data about the image pickup lens according tothe second embodiment. FIG. 3 is a cross-sectional view of the imagepickup lens. FIG. 4 shows various aberration diagrams.

TABLE 2 f = 5.372 F = 2.8 Surface Number r d nd ν K  1 (ST) 2.035 0.6051.497  81.60 0.145  2 −19.788 0.233 0  3 −4.221 0.295 1.6142 25.58−1.602  4 13.376 0.341 0  5 3.098 0.486 1.5247 56.26 −11.308  6 4.1400.731 0.271  7 −2.446 0.818 1.5247 56.26 −0.334  8 −1.493 0.239 −0.653 9 3.310 0.855 1.5247 56.26 −12.446 10 1.488 0.849 −4.788 11 ∞ 0.3001.5168 64.20 12 ∞ 0.803 Surface Number A4 A6 A8 A10 A12 A14 A16  1 (ST)−7.452E−3 −1.617E−4 −1.335E−2 4.383E−3 −9.221E−3 4.483E−3 −3.834E−3  21.998E−2 −2.240E−2 −1.467E−2 −1.152E−2 3.209E−3 0 0  3 1.470E−1−1.118E−1 5.112E−2 −1.648E−2 −1.373E−2 1.325E−2 0  4 9.526E−2 −4.060E−21.128E−2 1.414E−2 −1.462E−2 5.794E−3 0  5 −4.356E−2 −4.909E−3 −2.662E−32.513E−3 0 0 0  6 −4.106E−2 −3.596E−3 3.640E−7 6.811E−4 0 0 0  75.620E−2 −4.763E−2 2.579E−2 −7.309E−3 9.426E−4 0 0  8 3.109E−2 −6.202E−3−9.889E−4 1.388E−3 −1.345E−4 0 0  9 −7.078E−2 1.540E−2 −1.993E−34.351E−5 2.090E−5 1.538E−6 −1.030E−8 10 −4.561E−2 1.071E−2 −2.036E−32.488E−4 −1.998E−5 9.963E−7 −2.502E−8

Third Embodiment

Table 3 shows numerical data about the image pickup lens according tothe third embodiment. FIG. 5 is a cross-sectional view of the imagepickup lens. FIG. 6 shows various aberration diagrams.

TABLE 3 f = 5.269 F = 2.8 Surface Number r d nd ν K  1 (ST) 2.093 0.6081.5441 56.00 0.123  2 −25.611 0.211 0  3 −4.074 0.307 1.5850 30.00−1.357  4 11.977 0.336 0  5 3.166 0.478 1.5441 56.00 −11.659  6 4.0640.731 0.351  7 −2.478 0.790 1.5247 56.26 −0.290  8 −1.540 0.274 −0.648 9 3.353 0.859 1.5247 56.26 −12.746 10 1.488 0.794 −4.901 11 ∞ 0.3001.5168 64.20 12 ∞ 0.713 Surface Number A4 A6 A8 A10 A12 A14 A16  1 (ST)−8.004E−3 4.932E−5 −1.335E−2 4.345E−3 −9.202E−3 4.586E−3 −3.708E−3  21.747E−2 −2.375E−2 −1.468E−2 −1.094E−2 3.436E−3 0 0  3 1.466E−1−1.114E−1 5.110E−2 −1.663E−2 −1.384E−2 1.328E−2 0  4 9.639E−2 −4.030E−21.113E−2 1.390E−2 −1.439E−2 5.879E−3 0  5 −4.371E−2 −5.274E−3 −3.020E−32.317E−3 0 0 0  6 −4.084E−2 −3.546E−3 −2.715E−5 7.200E−4 0 0 0  75.558E−2 −4.774E−2 2.575E−2 −7.317E−3 9.431E−4 0 0  8 3.087E−2 −6.449E−3−1.021E−3 1.386E−3 −1.344E−4 0 0  9 −7.043E−2 1.531E−2 −2.006E−34.195E−5 2.091E−5 −1.493E−6 8.400E−10 10 −4.574E−2 1.069E−2 −2.047E−32.484E−4 −1.994E−5 1.002E−6 −2.527E−8

Fourth Embodiment

Table 4 shows numerical data about the image pickup lens according tothe fourth embodiment. FIG. 7 is a cross-sectional view of the imagepickup lens. FIG. 8 shows various aberration diagrams.

TABLE 4 f = 5.187 F = 2.7 Surface Number r d nd ν K  1 (ST) 2.119 0.6261.5441 56.00 0.177  2 −11.544 0.208 0  3 −3.147 0.298 1.5850 30.00−5.094  4 9.796 0.373 0  5 2.701 0.428 1.5441 56.00 −11.168  6 3.8420.837 0.129  7 −2.253 0.750 1.5247 56.26 −0.654  8 −1.467 0.401 −0.694 9 1.656 0.587 1.5247 56.26 −10.501 10 0.981 0.874 −4.578 11 ∞ 0.3001.5168 64.20 12 ∞ 0.742 Surface Number A4 A6 A8 A10 A12 A14 A16  1 (ST)−7.510E−3 1.743E−3 −1.246E−2 5.493E−3 −8.377E−3 4.978E−3 −3.500E−3  22.507E−2 −1.481E−2 −1.129E−2 −1.181E−2 3.172E−3 0 0  3 1.526E−1−1.113E−1 5.074E−2 −1.533E−2 −1.395E−2 1.133E−2 0  4 9.710E−2 −4.050E−21.124E−2 1.365E−2 −1.474E−2 5.407E−3 0  5 −3.599E−2 −8.738E−3 −4.179E−32.048E−3 0 0 0  6 −4.051E−2 −4.801E−3 −6.520E−4 5.650E−4 0 0 0  76.564E−2 −4.702E−2 2.607E−2 −7.359E−3 8.648E−4 0 0  8 3.490E−2 −3.356E−3−1.098E−3 1.296E−3 −1.421E−4 0 0  9 −7.077E−2 1.589E−2 −1.963E−34.145E−5 2.045E−5 −1.557E−6 −2.866E−9 10 −5.003E−2 1.088E−2 −1.968E−32.477E−4 −2.068E−5 9.622E−7 −1.548E−8

Fifth Embodiment

Table 5 shows numerical data about the image pickup lens according tothe fifth embodiment. FIG. 9 is a cross-sectional view of the imagepickup lens. FIG. 10 shows various aberration diagrams.

TABLE 5 f = 5.700 F = 2.8 Surface Number r d nd ν K  1 (ST) 1.974 0.7201.5311 56.00 0.260  2 −14.375 0.150 0  3 −4.100 0.350 1.6142 25.58 1.248 4 55.800 0.360 0  5 5.600 0.340 1.5311 56.00 −20.645  6 3.868 0.7501.356  7 −3.010 0.820 1.5311 56.00 −0.508  8 −1.634 0.270 −0.656  94.156 0.880 1.5311 56.00 −29.637 10 1.582 0.830 −5.617 11 ∞ 0.300 1.516864.20 12 ∞ 0.770 Surface Number A4 A6 A8 A10 A12 A14 A16  1 (ST)−6.011E−3 4.555E−3 −1.140E−2 5.896E−3 −7.660E−3 5.633E−3 −3.706E−3  23.346E−2 −2.148E−2 −1.342E−2 −1.061E−2 3.525E−3 0 0  3 1.407E−1−1.057E−1 4.976E−2 −1.790E−2 −1.431E−2 1.182E−2 0  4 1.000E−1 −4.704E−21.326E−2 1.542E−2 −1.468E−2 5.766E−3 0  5 −5.387E−2 −6.340E−3 −1.971E−32.628E−3 0 0 0  6 −4.023E−2 2.476E−4 1.005E−3 6.170E−4 0 0 0  7 5.679E−2−4.556E−2 2.594E−2 −7.443E−3 8.944E−4 0 0  8 3.073E−2 −5.791E−3−8.590E−4 1.367E−3 −1.517E−4 0 0  9 −6.996E−2 1.530E−2 −1.966E−35.619E−5 2.207E−5 −1.613E−6 −4.417E−8 10 −4.594E−2 1.064E−2 −2.039E−32.506E−4 −2.003E−5 9.526E−7 −2.202E−8

Sixth Embodiment

Table 6 shows numerical data about the image pickup lens according tothe sixth embodiment. FIG. 11 is a cross-sectional view of the imagepickup lens. FIG. 12 shows various aberration diagrams.

TABLE 6 f = 4.986 F = 2.8 Surface Number r d nd ν K  1 (ST) 2.084 0.6041.5311 56.00 0.168  2 −21.296 0.222 0  3 −3.958 0.300 1.6142 25.58−1.423  4 13.768 0.323 0  5 3.075 0.497 1.5311 56.00 −11.809  6 4.1390.624 0.275  7 −2.412 0.870 1.5247 56.26 −0.378  8 −1.484 0.208 −0.649 9 3.407 0.955 1.5247 56.26 −5.620 10 1.561 0.802 −4.276 11 ∞ 0.3001.5168 64.20 12 ∞ 0.674 Surface Number A4 A6 A8 A10 A12 A14 A16  1 (ST)−6.789E−3 2.618E−4 −1.386E−2 3.682E−3 −9.711E−3 4.535E−3 −2.955E−3  21.842E−2 −2.358E−2 −1.510E−2 −1.166E−2 3.030E−3 0 0  3 1.465E−1−1.117E−1 5.082E−2 −1.681E−2 −1.391E−2 1.334E−2 0  4 9.611E−2 −4.021E−21.153E−2 1.421E−2 −1.461E−2 5.550E−3 0  5 −4.518E−2 −5.504E−3 −2.914E−32.385E−3 0 0 0  6 −4.104E−2 −3.503E−3 −5.896E−5 6.932E−4 0 0 0  75.684E−2 −4.751E−2 2.584E−2 −7.290E−3 9.508E−4 0 0  8 3.092E−2 −6.249E−3−1.018E−3 1.379E−3 −1.373E−4 0 0  9 −6.971E−2 1.550E−2 −1.986E−34.363E−5 2.079E−5 −1.571E−6 −1.765E−8 10 −4.447E−2 1.070E−2 −2.036E−32.489E−4 −1.996E−5 1.000E−6 −2.448E−8

Table 7 below relates to the first to sixth embodiments and shows valuesfor conditional expressions (1) to (17) below.

Conditional expression (1) concerns the Abbe number of a material usedfor the first lens L1. Conditional expression (2) concerns the Abbenumber of a material used for the second lens L2.

45<ν1<90  Conditional expression (1)

22<ν2<35  Conditional expression (2)

where ν1 is the Abbe number for d-line of the first lens, and ν2 is theAbbe number for d-line of the second lens.

Conditional expression (3) defines the range of the focal length of thefirst lens L1 with respect to the focal length of the entire imagepickup lens system. Conditional expression (4) defines the range of thefocal length of the second lens L2 with respect to the focal length ofthe entire image pickup lens system.

0.5<f1/f<1.00  Conditional expression (3)

−1.50<f2/f<−0.65  Conditional expression (4)

where f is the composite focal length of the entire image pickup lenssystem, f1 is the focal length of the first lens, and f2 is the focallength of the second lens.

Conditional expression (5) defines the range of the focal length of thefourth lens L4 with respect to the focal length of the entire imagepickup lens system. Conditional expression (6) defines the range of thefocal length of the fifth lens L5 with respect to the focal length ofthe entire image pickup lens system.

0.9<f4/f<1.50  Conditional expression (5)

−1.70<f5/f<−0.85  Conditional expression (6)

where f is the composite focal length of the entire image pickup lenssystem, f4 is the focal length of the fourth lens, and f5 is the focallength of the fifth lens.

Conditional expression (7) defines the ratio between the focal length ofthe first lens L1 and the focal length of the third lens L3.

−0.15<f1/f3<0.37  Conditional expression (7)

where f1 is the focal length of the first lens, and f3 is the focallength of the third lens.

Conditional expression (8) defines the composite focal length of thesecond lens L2, the third lens L3, and the fourth lens L4.

0.0<f2·3·4  Conditional expression (8)

Conditional expression (9) defines the power relationship between thefirst lens L1, the second lens L2, and the third lens L3, that is, thefocal length relationship. Conditional expression (10) defines the powerrelationship between the first lens L1, the third lens L3, and thefourth lens L4, that is, the focal length relationship. Conditionalexpression (11) defines the power relationship between the first lensL1, the third lens L3, and the fifth lens L5, that is, the focal lengthrelationship.

f1<|f2|<|f3|  Conditional expression (9)

f1<f4<|f3|  Conditional expression (10)

f1<|f5|<|f3|  Conditional expression (11)

Conditional expression (12) defines the lens shape of the first lens L1.

−0.40<r1/r2<0.10  Conditional expression (12)

where r1 is the curvature radius of the object-side surface of the firstlens, and r2 is the curvature radius of the image-side surface of thefirst lens.

Conditional expression (13) defines the lens shape of the fourth lensL4.

1.4<r7/r8<3.0  Conditional expression (13)

where r7 is the curvature radius of the object-side surface of thefourth lens, and r8 is the curvature radius of the image-side surface ofthe fourth lens.

Conditional expression (14) defines the optical length with respect tothe focal length.

1.05<L/f<1.30  Conditional expression (14)

where L is the distance from the front surface of the first lens to theimage plane, and f is the composite focal length of the entire imagepickup lens system.

Conditional expression (15) defines the F-number (Fno), which is anindication of lens brightness.

0.30<CA1/f<0.50  Conditional expression (15)

where CA1 is the diameter of the aperture stop, and f is the compositefocal length of the entire image pickup lens system.

Conditional expression (16) defines the range of the focal length of thesecond lens L2 with respect to the focal length of the entire imagepickup lens system, and relates to a case where more stringentconditions than those defined by conditional expression (4) aresatisfied.

−1.30<f2/f<−0.75  Conditional expression (16)

where f is the composite focal length of the entire image pickup lenssystem, and f2 is the focal length of the second lens.

Conditional expression (17) defines the lens shape of the fourth lens L4and relates to a case where more stringent conditions than those definedby conditional expression (13) are satisfied.

1.45<r7/r8<2.0  Conditional expression (17)

where r7 is the curvature radius of the object-side surface of thefourth lens, and r8 is the curvature radius of the image-side surface ofthe fourth lens.

TABLE 7 First Second Third Fourth Fifth Sixth Embodiment EmbodimentEmbodiment Embodiment Embodiment Embodiment Conditional 56.26 81.6056.00 56.00 56.00 56.00 Expression (1) Conditional 25.58 25.58 30.0030.00 25.58 25.58 Expression (2) Conditional 0.909 0.698 0.680 0.6450.582 0.723 Expression (3) Conditional −1.205 −0.966 −0.979 −0.778−1.089 −0.997 Expression (4) Conditional 1.300 1.050 1.141 1.163 0.9781.115 Expression (5) Conditional −1.671 −1.144 −1.150 −1.262 −0.957−1.340 Expression (6) Conditional 0.346 0.185 0.162 0.226 −0.131 0.186Expression (7) Conditional 10.266 10.597 13.323 15.698 18.816 10.806Expression (8) Conditional Expression (9) f1 4.379 3.747 3.584 3.3443.319 3.606 |f2| 5.800 5.191 5.160 4.037 6.205 4.973 |f3| 12.647 20.21422.174 14.764 25.268 19.382 Conditional Expression (10) f1 4.379 3.7473.584 3.344 3.319 3.606 f4 6.258 5.638 6.011 6.033 5.577 5.558 |f3|12.647 20.214 22.174 14.764 25.268 19.382 Conditional Expression (11) f14.379 3.747 3.584 3.344 3.319 3.606 |f5| 8.045 6.144 6.059 6.546 5.4576.680 |f3| 12.647 20.214 22.174 14.764 25.268 19.382 Conditional 0.000−0.103 −0.082 −0.184 −0.137 −0.098 Expression (12) Conditional 1.5451.638 1.609 1.536 1.842 1.625 Expression (13) Conditional 1.292 1.2201.215 1.238 1.147 1.279 Expression (14) Conditional 0.357 0.355 0.3570.385 0.355 0.355 Expression (15)

As shown in Table 7, the first to sixth embodiments of the presentinvention satisfy all of conditional expressions (1) to (17).Conditional expressions (1) and (2) define the Abbe number of the firstlens L1 and the second lens L2, respectively. If the value is below thelower limit of the conditional expression (1), the variance valuedifference from the second lens is decreased so that chromaticaberration correction is insufficient. If, on the contrary, the valueexceeds the upper limit thereof, the balance between axial chromaticaberration and chromatic aberration of magnification is impaired so thatperformance deterioration occurs at the periphery of an image area. Ifthe value is below the lower limit of the conditional expression (2),the balance between axial chromatic aberration and off-axis chromaticaberration is impaired so that performance deterioration occurs at theperiphery of the image area. If, on the contrary, the value exceeds theupper limit thereof, the variance value difference from the first lensis decreased so that chromatic aberration correction is insufficient.However, when conditional expressions (1) and (2) are satisfied, aproper balance is maintained between axial chromatic aberration andchromatic aberration of magnification. This makes it possible to preventperformance deterioration at the periphery of the image area and provideexcellent chromatic aberration correction.

Conditional expressions (3) and (4) define the range of the focal lengthof the first lens L1 and the second lens L2, respectively, with respectto the focal length of the entire image pickup lens system. If the valueis below the lower limit of the conditional expression (3), the focallength of the first lens L1 is too short. This makes it difficult tocorrect spherical aberration and coma aberration. If, on the contrary,the value exceeds the upper limit thereof, the optical length is toolong so that the thickness of the image pickup lens cannot besufficiently reduced. If the value is below the lower limit of theconditional expression (4), the power of the second lens L2 isinsufficient so that chromatic aberration cannot be adequatelycorrected. If, on the contrary, the value exceeds the upper limitthereof, the focal length of the second lens L2 is too short. This makesit difficult to correct spherical aberration and coma aberration, andthe error sensitivity during manufacturing becomes severe. However, whenconditional expressions (3) and (4) are satisfied, it is possible toproperly correct spherical aberration and coma aberration. Further, thepower of the second lens L2 becomes sufficient, making it possible toproperly correct chromatic aberration, spherical aberration, and comaaberration.

Conditional expression (5) defines the range of the focal length of thefourth lens L4 with respect to the focal length of the entire imagepickup lens system. If the value is below the lower limit of theconditional expression (5), the focal length of the fourth lens L4 istoo short. This makes it difficult to correct astigmatism and comaaberration, and the error sensitivity during manufacturing becomessevere. If, on the contrary, the value exceeds the upper limit thereof,chromatic aberration of magnification and astigmatism are not adequatelycorrected so that expected performance is not obtained. However, whenconditional expression (5) is satisfied, it is easy to correctastigmatism, coma aberration, and chromatic aberration of magnification.This makes it possible to obtain expected performance.

Conditional expression (6) defines the range of the focal length of thefifth lens L5 with respect to the focal length of the entire imagepickup lens system. If the value is below the lower limit of theconditional expression (6), the power of the fifth lens L5 isinsufficient. This makes it difficult to decrease the optical length.If, on the contrary, the value exceeds the upper limit thereof, it isdifficult to decrease the CRA, and the error sensitivity at low imageheight during manufacturing becomes severe. However, when conditionalexpression (6) is satisfied, the fifth lens L5 has a sufficient power,making it possible to reduce the optical length. This makes it easy todecrease the CRA so that the error sensitivity at low image heightduring manufacturing improves.

Conditional expression (7) defines the ratio between the focal length ofthe first lens L1 and the focal length of the third lens L3. If thevalue is below the lower limit of the conditional expression (7), thefocal length of the third lens L3 is negative and too short. This makesit difficult to provide aberration correction. If, on the contrary, thevalue exceeds the upper limit thereof, the focal length of the thirdlens L3 is positive and too short. This impairs the balance ofastigmatism and the balance of coma aberration, and the errorsensitivity during manufacturing becomes severe. However, whenconditional expression (7) is satisfied, it is easy to provideaberration correction. Further, it is possible to prevent the focallength of the third lens L3 from being too short, and to maintain anexcellent astigmatism balance and coma aberration balance.

Conditional expression (8) defines the composite focal length of thesecond lens L2, the third lens L3, and the fourth lens L4. If the valueis below the lower limit of the conditional expression (8), the negativepower of the second lens L2 is too strong so that the error sensitivityduring manufacturing becomes too severe, or the positive power of thefourth lens L4 is too weak so that it is difficult to correctastigmatism and distortion. However, when conditional expression (8) issatisfied, it is easy to correct astigmatism and distortion.

Conditional expression (9) defines the power relationship between thefirst lens L1, the second lens L2, and the third lens L3, that is, thefocal length relationship. If the value is below the lower limit of theconditional expression (9), the negative power of the second lens L2 istoo strong, so that the optical length becomes long, and the errorsensitivity during manufacturing becomes severe. If, on the contrary,the value exceeds the upper limit thereof, the power of the third lensL3 is too strong so that it is difficult to obtain adequate off-axisperformance. However, when conditional expression (9) is satisfied, itis possible to decrease the optical length and easily obtain adequateoff-axis performance.

Conditional expression (10) defines the power relationship between thefirst lens L1, the third lens L3, and the fourth lens L4, that is, thefocal length relationship. If the value is below the lower limit of theconditional expression (10), the power of the fourth lens L4 is toostrong, so that the optical length becomes long, and it is difficult tocorrect astigmatism and distortion. If, on the contrary, the valueexceeds the upper limit thereof, the power of the third lens L3 is toostrong so that it is difficult to obtain adequate off-axis performance.However, when conditional expression (10) is satisfied, it is easy tocorrect astigmatism and distortion and obtain adequate off-axisperformance.

Conditional expression (11) defines the power relationship between thefirst lens L1, the third lens L3, and the fifth lens L5, that is, thefocal length relationship. If the value is below the lower limit of theconditional expression (11), the negative power of the fifth lens L5 istoo strong. This makes it difficult to correct coma aberration andastigmatism. If, on the contrary, the value exceeds the upper limitthereof, the power of the third lens L3 is too strong so that it isdifficult to obtain adequate off-axis performance. However, whenconditional expression (11) is satisfied, it is easy to correct comaaberration and astigmatism and obtain adequate off-axis performance.

Conditional expression (12) defines the lens shape of the first lens L1.If the value is below the lower limit of the conditional expression(12), the optical length cannot be readily reduced. In addition, theerror sensitivity during the manufacture of the first lens L1 becomessevere. If, on the contrary, the value exceeds the upper limit thereof,it is difficult to maintain a proper aberration balance so that expectedperformance is not obtained. However, when conditional expression (12)is satisfied, the optical length can be readily reduced. In addition, itis possible to maintain a proper aberration balance and obtain expectedperformance.

Conditional expression (13) defines the lens shape of the fourth lensL4. If the value is below the lower limit of the conditional expression(13), the power of the fourth lens L4 is too weak. Consequently,performance deterioration occurs because it is difficult to correctvarious aberrations. If, on the contrary, the value exceeds the upperlimit thereof, the fourth lens L4 has an excessively strong power or hasa small degree of meniscus curvature. In this instance, too, it isdifficult to maintain a proper aberration balance so that expectedperformance is not obtained. However, when conditional expression (13)is satisfied, it is easy to correct various aberrations and maintain aproper aberration balance. As a result, expected performance isobtained.

Conditional expression (14) defines the optical length with respect tothe focal length of the entire image pickup lens system. If the value isbelow the lower limit of the conditional expression (14), it isdifficult to correct various aberrations due to an excessively decreasedoptical length. In addition, the error sensitivity during manufacturingbecomes too severe. If, on the contrary, the value exceeds the upperlimit thereof, it is difficult to reduce the thickness of the imagepickup lens due to an excessively increased optical length. However,when conditional expression (14) is satisfied, it is easy to correctvarious aberrations. In addition, the thickness of the image pickup lenscan be readily reduced because the optical length is not excessivelyshort.

Conditional expression (15) defines the F-number (Fno), which is anindication of lens brightness. If the value is below the lower limit ofthe conditional expression (15), the F-number is excessively large sothat requested brightness is not achieved in most cases. If, on thecontrary, the value exceeds the upper limit thereof, the F-number isexcessively small or the distance between the aperture stop (F-numberluminous flux restriction plate) and the front surface of the first lensL1 is excessively long. In either case, expected optical performance isnot obtained. However, when conditional expression (15) is satisfied,the expected optical performance can be obtained with ease.

Further, the second lens L2, the third lens L3, the fourth lens L4, andthe fifth lens L5 are so-called plastic lenses that have at least oneaspherical surface and are made of a resin material. Cost reduction canbe achieved when at least the second lens L2, the third lens L3, thefourth lens L4, and the fifth lens L5 are made of an inexpensive resinmaterial exhibiting high production efficiency.

Furthermore, as the aperture stop ST is positioned on the object side ofthe first lens L1 to decrease the CRA (Chief Ray Angle), it is easy toreduce the CRA (Chief Ray Angle) and obtain sufficient light amount atthe periphery of the image plane at which light amount decreases.

Moreover, as the object side surface and image side surface of the fifthlens L5 have an aspherical shape that contains at least one inflectionpoint from the center of the lens to the periphery thereof, it ispossible to obtain adequate off-axis performance and CRA.

While the present invention has been described in terms of exemplaryembodiments, it should be understood that the invention is not limitedto those exemplary embodiments. Those skilled in the art will understandthat various changes and modifications can be made within the scope andspirit of the invention.

The effects of the present invention are as follows.

The image pickup lens according to the present invention includes fivelenses (the first to fifth lenses). Further, the third lens plays a rolethat is not found in a conventional four-lens configuration. Therefore,the present invention makes it possible to provide a high-performance,low-cost, compact lens in which various aberrations are properlycorrected to support large-size, high-resolution image pickup elementshaving highly minute pixels.

What is claimed is:
 1. An image pickup lens for a solid-state imagepickup element, consisting of, in the order from an object side: a firstlens, which has a convex surface facing the object side on an opticalaxis and has a positive refractive power; a second lens, which has aconcave surface facing an image side on the optical axis and has anegative refractive power; a third lens, which has a convex surfacefacing the object side on the optical axis and has a meniscus shape; afourth lens, which has a convex surface facing the image side on theoptical axis, has a positive refractive power, and has a meniscus shape;and a fifth lens, which has a concave surface facing the image side onthe optical axis and has a negative refractive power; wherein theobject-side surface and the image-side surface of the fifth lens have anaspherical shape that contains at least one inflection point from thecenter of the lens to the periphery thereof; and the curvature radius ofthe fourth lens satisfies conditional expression (13) below:1.4<r7/r8<3.0  (13) where r7 is the curvature radius of the object-sidesurface of the fourth lens, and r8 is the curvature radius of theimage-side surface of the fourth lens.
 2. The image pickup lensaccording to claim 1, wherein the Abbe number of a material used for thefirst lens and the second lens satisfies conditional expressions (1) and(2) below:45<ν1<90  (1)22<ν2<35  (2) where ν1 is the Abbe number for d-line of the first lens,and ν2 is the Abbe number for d-line of the second lens.
 3. The imagepickup lens according to claim 1, wherein the first lens, the secondlens, the third lens, the fourth lens, and the fifth lens are so-calledplastic lenses that have at least one aspherical surface and are made ofa resin material.
 4. The image pickup lens according to claim 1, whereinan aperture stop is positioned on the object side of the first lens. 5.The image pickup lens according to claim 1, wherein the first lens andthe second lens satisfy conditional expressions (3) and (4) below:0.5<f1/f<1.00  (3)−1.50<f2/f<−0.65  (4) where f is the composite focal length of theentire image pickup lens system, f1 is the focal length of the firstlens, and f2 is the focal length of the second lens.
 6. The image pickuplens according to claim 1, wherein the fourth lens and the fifth lenssatisfy conditional expressions (5) and (6) below:0.9<f4/f<1.50  (5)−1.70<f5/f<−0.85  (6) where f is the composite focal length of theentire image pickup lens system, f4 is the focal length of the fourthlens, and f5 is the focal length of the fifth lens.
 7. The image pickuplens according to claim 1, wherein the second lens, the third lens, andthe fourth lens satisfy conditional expression (8) below:0.0<f2·3·4  (8) where f2·3·4 is the composite focal length of thesecond, third, and fourth lenses.
 8. The image pickup lens according toclaim 1, wherein the first lens, the second lens, the third lens, thefourth lens, and the fifth lens satisfy conditional expressions (9),(10), and (11) below:f1<|f2|<|f3|  (9)f1<f4<|f3|  (10)f1<|f5|<|f3|  (11) where f1 is the focal length of the first lens, f2 isthe focal length of the second lens, f3 is the focal length of the thirdlens, f4 is the focal length of the fourth lens, and f5 is the focallength of the fifth lens.
 9. The image pickup lens according to claim 8,wherein the curvature radius of the first lens satisfies conditionalexpression (12) below:−0.40<r1/r2<0.10  (12) where r1 is the curvature radius of theobject-side surface of the first lens, and r2 is the curvature radius ofthe image-side surface of the first lens.
 10. The image pickup lensaccording to claim 8, wherein the optical length and focal length of theentire image pickup lens system satisfy conditional expression (14)below:1.05<L/f<1.30  (14) where L is the distance from a front surface of thefirst lens to an image plane, and f is the composite focal length of theentire image pickup lens system.
 11. The image pickup lens according toclaim 4, wherein the diameter of the aperture stop satisfies conditionalexpression (15) below:0.30<CA1/f<0.50  (15) where CA1 is the diameter of the aperture stop,and f is the composite focal length of the entire image pickup lenssystem.
 12. The image pickup lens according to claim 8, wherein the Abbenumber of a material used for the first lens and the second lenssatisfies conditional expressions (1) and (2) below:45<ν1<90  (1)22<ν2<35  (2) where ν1 is the Abbe number for d-line of the first lens,and ν2 is the Abbe number for d-line of the second lens.
 13. The imagepickup lens according to claim 8, wherein the first lens, the secondlens, the third lens, the fourth lens, and the fifth lens are so-calledplastic lenses that have at least one aspherical surface and are made ofa resin material.
 14. The image pickup lens according to claim 8,wherein an aperture stop is positioned on the object side of the firstlens.